<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script>
        var num = 1 ;
        var arr = ["../image/banner/banner_1.jpg","../image/banner/banner_2.jpg","../image/banner/banner_3.jpg"];
        function fun() {
            num++;
            var img = document.getElementById("img");
            img.src = arr[num % 3];
        }
        setInterval(fun, 3000);
    </script>
</head>
<body>

<img src="../image/banner/banner_1.jpg" width="100%" id="img">

</body>
</html>